Slow Dynamics of Lymphoscintigraphic Mapping Is Associated to the Negativity of the Sentinel Node in Melanoma Patients

Abstract

To confirm an association between a slow kinetics in the lymphoscintigraphic mapping of the sentinel node (SN), and SN negativity (SN-) in melanoma (MM) patients, and to test whether a long scintigraphic appearance time (SAT) could be a noninvasive surrogate marker of SN-. A retrospective cohort of 194 successive MMs with Breslow >/=1.5 mm with follow-up >18 months after SN procedure were retrospectively randomized into two groups: a test sample (T) (two-thirds) to assess the relationship between SN status and lymphoscintigraphy dynamics, and to identify a potential scintigraphic marker of SN-, which was confirmed in the validation sample (V) (one-third). A prospective cohort of 150 consecutive new patients was then used to test the negative predictive value (NPV) of this marker. In sample T, SAT was significantly lower in SN+ than SN- patients (p = 0.04). In a multivariate model, SAT was predictive of SN status, before tumor thickness. SAT was also predictive of disease of disease-free survival (DFS) and overall survival (OS). None of the patients with SAT >30 min (24.8%) were SN+. SAT >30 min was validated as a potential marker for SN- in sample V with NPV = 100% (confidence interval [CI] 84.6-100). In the prospective cohort, the NPV of this marker was however only 84.6% (CI 65.1-95.6). Slow SAT is associated with SN- and better survival, which opens interesting hypotheses as to the process of the first nodal metastasis. However, the best possible lymphoscintigraphic marker was not consistent enough to recognize patients in whom the invasive phase of SN biopsy could be avoided.